Under high-speed cutting (HSC) conditions, the dynamic performance of tool holders directly determines machining stability, surface quality, tool life and spindle reliability. This paper focuses on the dynamic behavior of tool holders during high-speed rotation and cutting, including stiffness, natural frequency, damping characteristics, dynamic balance, radial runout and vibration response. Key influencing factors such as material properties, structural parameters, spindle-holder interface, overhang length and clamping mechanism are analyzed. Through finite element simulation and experimental comparison, the dynamic performance of different tool holder structures is evaluated. The results provide a theoretical basis for structural optimization, model selection and processing parameter matching of tool holders in high-speed machining systems.

1. Introduction

High-speed cutting is characterized by high rotational speed, high feed rate and high material removal rate. The tool holder, as the critical component connecting the spindle and cutting tool, bears complex loads including centrifugal force, cutting force impact, thermal load and dynamic excitation.

Poor dynamic performance may lead to chatter, excessive runout, tool wear acceleration and even spindle damage. Therefore, systematic dynamic performance analysis of tool holders is essential for improving machining accuracy, stability and overall efficiency in modern CNC machining.

2. Key Dynamic Performance Indicators

2.1 Static and Dynamic Stiffness

Stiffness reflects the ability to resist deformation under cutting forces and centrifugal loads. Low stiffness leads to large deflection, reduced machining accuracy and increased vibration tendency.

2.2 Natural Frequency and Mode Shapes

The natural frequency of the tool holder-spindle system determines its sensitivity to resonance. If the excitation frequency approaches the natural frequency, severe vibration and chatter will occur.

2.3 Damping Characteristics

Damping determines the ability to dissipate vibration energy. Higher damping helps suppress chatter and improve stability in high-speed cutting.

2.4 Dynamic Balance Quality

Unbalanced mass causes periodic radial force at high speeds, resulting in vibration, noise and reduced bearing life.

2.5 Radial Runout and Concentricity

Runout directly affects surface roughness, dimensional error and tool wear uniformity. It is particularly critical in finish milling and precision machining.

3. Influencing Factors of Dynamic Performance

3.1 Structural Parameters

Overhang length, diameter ratio, wall thickness and overall shape significantly affect stiffness and natural frequency. Longer overhang greatly reduces dynamic stability.

3.2 Material Properties

Elastic modulus, density, damping capacity and fatigue strength influence stiffness-to-mass ratio and vibration response.

3.3 Spindle–Tool Holder Interface

Taper fitting accuracy, contact pressure and friction characteristics determine the overall rigidity of the system. Poor interface matching causes obvious vibration and loss of precision.

3.4 Clamping Mechanism

Collet, hydraulic expansion, heat-shrink and milling chuck types show differences in clamping uniformity, repeat positioning accuracy and damping performance.

3.5 Thermal Effects

High-speed cutting generates heat that causes thermal expansion, changing contact conditions and dynamic stiffness, which further affects stability.

4. Analysis Methods

4.1 Finite Element Simulation (FEA)

Used to simulate modal characteristics, stress distribution, deformation and vibration response under high-speed rotation.

4.2 Modal Testing

Experimental modal analysis obtains natural frequency, damping ratio and mode shapes to verify simulation accuracy.

4.3 Dynamic Cutting Test

Under actual machining conditions, vibration acceleration, cutting force and surface roughness are measured to evaluate real dynamic performance.

4.4 High-Speed Rotation Dynamic Balance Test

Detects unbalance amount and evaluates vibration characteristics under actual working speed.

5. Results and Performance Evaluation

Through dynamic analysis, the following conclusions can be drawn:

Reasonable structural design can significantly improve natural frequency and avoid resonance zones.

High-damping materials and optimized interfaces effectively suppress vibration amplitude.

Dynamic balance significantly reduces vibration under high-speed conditions.

Heat-shrink and hydraulic tool holders generally show better dynamic performance than traditional collet holders.